We have developed two rigorous model systems for studies of specific interactions between membranes. The first system involves the use of liposome model membranes onto which Alpha-bungarotoxins covalently coupled with palmitic acid have been attached. The toxin-liposomes specifically bind with the microsac membrane vesicles highly enriched with the nicotinic acetylcholine receptors and cause an inhibition of the agonist-dependent cation flux of the microsacs. The affinity of liposome-microsac binding is a sensitive function of the surface density of the toxin molecules on the liposomes. In the second system, we have covalently attached the wheat germ agglutinin (WGA) tothe liposomes. The WGA-liposomes showed much higher activity to agglutinate erythrocytes than the free WGA. They also showed approximately 50-fold higher binding activity to the mouse splenocytes when compared with the protein-free liposomes. We plan to extend these observations to achieve the following goals: (1) to characterize by fluorescence spectroscopy and differential scanning calorimetry, the fatty acid derivatives of Alpha-bungarotoxin and their interactions with the lipid bilayer, (2) to measure by light-scattering the binding of microsacs with toxin-liposomes of different surface densities and different rotational and lateral mobilities of the toxin molecules, (3) to determine the thermodynamic and kinetic properties of the above binding, (4) to measure the binding of WGA-liposomes with rat hepatoma H-35 cells as functions of the surface density and mobility of the lectin molecules on the liposomes, (5) to measure the ability of the liposome-bound WGA to stimulate the insulin binding, to induce the tyrosine aminotransferase activity and to alter the surface distribution of membrane components in H-35 cells. These studies will provide fundamental information about the biophysical principles underlying the specific interactions between membranes. They may also shed some light on the molecular events involved in membrane interactions, cellular recognitions and cell-cell adhesions. The studies on the interactions of fatty acid-containing proteins with the lipid bilayers may provide insightful information on how this class of membranous macromolecules interacts with biological membranes.